A; 21 OBSERVATIONS ON GIGANTIOPS DESTRUCTOR FABRICIUS AND OTHER LEAPING ANTS' WILLIAM MORTON WHEELER. [Reprinted from BIOLOGICAL BULLETIN, Vol. XLII., No, 4, April, 1922.) [Reprinted from BIOLOGICAL BULLETIN, Vol. XLII., No. 4, April, 1922.1 OBSERVATIONS ON GIGANTIOPS DESTRUCTOR FABRICIUS AND OTHER LEAPING ANTS'. 1 WILLIAM MORTON WHEELER. In any study of the very exuberant ant-fauna of the Neotropical Region one can not fail to be impressed by the striking contrast between certain genera like Eciton, Pseudomyrma, Solenopsis, Crematogaster, Cryptocercus, Azteca, and Camponotus, each rep- resented by a large number of variable species, and genera like Paraponera, Acanthognathus, Daceton, Blepharidatta, Stegomyr- mex, and Gigantiops, each represented by a single, very stable species. Of course, such monotypic groups may be regarded either as very ancient, embracing during some former age many species of which only one has survived, or as single species which, after acquiring generic status in the remote past, have since under- gone little or no modification. The individuals of a species repre- senting a monotypic genus may be either very rare or local, mere relicts of a bygone age, or prominent and ubiquitous over larger geographical areas. This is true of such ants as Paraponera clavata Fabr. and Gigantiops destructor, which I have recently had abundant opportunity to study in the jungle about the Tropical Laboratory of the New York Zoological Society at Kartabo, Brit- ish Guiana. As the latter species is the more imperfectly known, I have singled it out for special consideration. The name Gigantiops destructor conjures up visions of a huge- eyed, insatiable monster, a kind of Cyclopean insect-jaguar. Fa- bricius, when he first described the insect in 1804 as Formica destructor, certainly knew nothing of its behavior and probably gave it what seemed to him an appropriate specific name for any ant measuring a centimeter in length. More than half a century later ('58) Frederick Smith received specimens taken by Bates at Ega, Brazil, and believed them to represent a new species which he described as Formica solitaria. The following note was appended i Contributions from the Entomological Laboratory of the Bussey Institu- tion, Harvard University. No. 177. 185 1 86 WILLIAM MORTON WHEELER. to the description: "This is a very remarkable insect; for inde- pendent of the enormously developed eyes and produced clypeus, the palpi are elongated to half the length of the thorax, the max- illary are six-, and the labial four-jointed. Mr. Bates says : "This curious solitary ant is never seen by more than one at a time, prowling about fallen leaves, etc., in the forest ; I have never seen its formicarium and, from its solitary habits, have no clue to guide me in looking for it." Perhaps Smith was confirmed in his choice of the specific name by the monastic or ascetic appearance of the insect, its somber black livery, relieved only by the golden- yellow tips of its antennae, its long, emaciated limbs and its huge eyes, perpetually dilated as if in astonishment and chagrin at the indecent behavior of other insects. Two short notes, however, by later observers indicate that Gigantiops may be neither an insatiable assassin nor a humble anchorite, but a harmless and perhaps rather frivolous creature, that may have become permanently goggle-eyed through an age- long endeavor to enjoy to the full the riotous beauties of its en- vironment. Emery ('93) was informed by Albert Schulz that the " Brazilian ant, Gigantiops destructor Fabr., which is distinguished by its enormous eyes, leaps from twig to twig, like the Odonto- machus hcematodes living in the same places," and Mann (1916) says : " In life this is one of the most attractive ants encountered. It lives always in the forest, where it forages either among the branches of trees or on ^he ground. The movements of the forag- ing worker are rapid, comparable to some of our species of Cicin- dela, and the bicolored antennae are kept constantly in motion." Roger ('63) was the first to throw Smith's Formica solitaria into the synonymy and to establish the peculiar genus Gigantiops. In more recent myrmecological literature mention of the insect recurs sporadically and at long intervals, showing that it was rarely seen in the many collections of South American ants examined by Mayr, Forel, Emery, Santschi, and others. Its known range, as indicated by the literature and by specimens in my collection, is as follows : Brazil: Ega (Bates) ; Para (E. Goeldi, ex coll. Forel) ; Maran- hao (Ducke) ; Para, Abuna, Porto Velho, and Madeira-Mamore R. R. (W. M. Mann).. OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. 187 French Guiana (Jelski). British Guiana: Kaieteur Falls, Tukheit, and Tumatumari .(F. E. Lutz) ; Penal Settlement, Bartica District (W. Beebe) ; Kar- tabo and Kalacoon (Wheeler) . Peru: Callanga (S'taudinger). Bolivia: Rio Beni (L. Balzan). These localities show that Gigantiops has. a very limited range compared with many Neotropical ants, since it is confined to a strip of South America east of the Andes and extending from about 10 north to 10 south of the equator. 1 Gigantiops (Fig. i) is a common ant in the forested portions of British Guiana, preferring 'shady places rather free from under- growth and spending most of its time on the ground, running over the dead leaves. It occurs singly, as stated by previous observers, and really belongs to a forest-floor ant-fauna comprising also Neoponera apicalis Latr., obscuricornis Emery and commutata Roger, Mesoponera constricta Mayr, Pachycondyla crassinoda La- treille and harp ax Fabr., Paraponera clavata Fabr., and Ectatomma quadridens Fabr. Those who are interested in mimicry will ob- serve that in its form, the dull black color of its body and yellow antennal tips, Gigantiops bears such a striking resemblance to N. apicalis and obscuricornis that the latter might be regarded as 1 1 find a note by von Motschulsky in a letter published in his " Etudes Entomologiques " (1855) and referred to in the "Stettiner Entomologische Zeitung " (1859), which seems to apply to Gigantiops, Speaking of the insects which he observed at Obispo, Panama, he says : " I observed a lot of ants of diverse and bizarre form, among others one bearing the closest resemblance to a spider, especially to a Salticus, and as it also has the ability to leap, I have named it Salticomorpha nigra." There are two objections to accepting the name Salticomorpha as antedating Gigantiops: first, there is no record of this insect's having been taken in Central America or even in Colombia, and second, von Motschulsky may have seen a Pseudomyrma gracilis Fabr., which resembles a black Attid spider in form and color, and have mistaken its erratic movements for leaps. The well-known arachnologist, E. Simon (in Emery, "Voyage de M. E. Simon" (Dec., i887-Avril, 1888). Formicides, Ann. Soc. Ent. France 1890, p. 65 nota) noticed that " all the species of the genus Pseudomyrma reproduce exactly the forms and colors of the spiders of the genus Simonella Peckh. (Attidae) and the resemblance is equally striking in their gait." For the present it seems advisable, therefore, either to treat Salticomorpha nigra Motsch, as a nomen midum or to include it with a query in the synonymy of Gigantiops destructor Fabr. i88 WILLIAM MORTON WHEELER. its models. Furthermore, these Ponerines sting very severely, whereas Gigantiops can be picked up with impunity. In Kartabo, nevertheless, the models are much less frequently seen than the mimic. This is interesting in connection with the observations of Mr. Tee Van, who finds that in the same region many of the FIG. i. Gigantiops destructor Fabr. Worker, about twice natural size ; dorsal and lateral views and head from above. mimetic butterflies are much more abundant than their putative Heliconid models. It would be a mistake to suppose that Gi- gantiops acts as if it derived any benefit from its striking resem- blance to the stinging Ponerines. It greatly surpasses them in agility and when pursued will even leap several inches in a very graceful, cat-like manner. On the rather infrequent occasions when it climbs onto bushes and is running over their foliage it will, if disturbed, leap, without the slightest hesitation, to another leaf or even to the ground and make off with great alacrity. When two Gigantiops happen to meet face to face, they exhibit a peculiar play. After stroking each other's heads for a moment with the yellow tips of their antennae, they move from side to side, precisely like two persons who meet on the sidewalk and try to prevent each other from passing. OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. 189 On rare occasions Gigantiops may be seen carrying a termite worker or other small insect in its jaws, but even such individuals are not easily followed to their nests. Forel's placing of this ant in his tribe (Ecophyllini, i.e., with (Ecophylla smaragdina Fabr., the well-known tree-ant of the Old World tropics, naturally led me to suppose that the nest must be in the trees, but this supposi- tion, which has probably been shared by other myrmecologists, proves to be erroneous. On July 14, after much careful search and persistent following of single workers, my son Ralph suc- ceeded in finding a nest in a partly decayed log only three or four inches in diameter lying on the ground at the edge of the Puruni trail and brought the portion inhabited by the ants into the labo- ratory. As soon as I began to dig into their nest the workers leaped out and made off, holding their larvae in their mandibles. The colony comprised only fifty or sixty workers, which had been living in some large cavities made by Passalus or other wood- inhabiting beetles. In one of the chambers there were empty cocoons, showing that the pupae of Gigantiops are not nude as in (Ecophylla, its supposed nearest ally among the Formicinae. I failed to secure the queen and believe she must have escaped un- observed among the workers. From these she differs merely in her somewhat larger size and slightly more voluminous thorax. Notwithstanding careful search by my son and myself, ten days elapsed before I could again observe a Gigantiops nest. I found the second nest in a similar situation, in a partly decayed piece of a Cecropia trunk about a foot and a half long and three inches in diameter, lying loosely on the dead leaves in the shade of a bush. I noticed one of the workers timidly guarding a small hole and hastily retreating into it on my approach. The hole was plugged with cotton and the log carried back to the laboratory. In order that the ants might not elude me as on the previous occasion, I opened the log over a pail of water, but notwithstanding these precautions a few of the workers managed to escape. The entire colony, which was inhabiting one of the large internodal cavities so peculiar to Cecropia, was scarcely larger than the former colony, but contained more larvae and several freshly spun worker cocoons. 1 90 WILLIAM MORTON WHEELER. No males were present and future attempts to find them and other colonies were unsuccessful. 1 Two matters call for further discussion in connection with the foregoing observations, the taxonomic affinities of Gigantiops de- structor and its modus saltandi. The generally accepted view of its taxonomic position can be traced to the various papers which Forel has published from time to time on the classification of the subfamily Formicinse (= Camponotinse Forel) . In 1878 he placed the genus Gigantiops between Opisthopsis and CEcophylla in his first tribe of the subfamily. In his classification of 1893 he omitted all mention of Gigantiops, though he enumerated the vari- ous other genera of the subfamily. In 1912 he remodeled .the classification and considerably augmented the number of tribes, to one of which, the CEcophyllini, he assigned the three genera Gigantiops, Myrmecorhynchus, and CEcophylla. The same arrange- ment is preserved in his paper of 1917. I endeavored to show in the same year that Myrmecorhynchus could not be retained among the CEcophyllini, but should probably constitute an independent tribe, the Myrmecorhynchini. The characters of the CEcophyllini, according to Forel, are the following: gizzard long and narrow, with straight calyx; clypeal fossa mo're or less distinct from the antennary fossa; antennas inserted a little behind the frontal area, but near the anterior ends of the frontal carinae. The gizzard characters are not peculiar to this tribe, but recur also in the Camponotini, and the remaining characters are decidedly weak, since they depend on slight differences in the proportions of the anterior portions of the head. When we compare Gigantiops with CEcophylla we are struck by the great differences in the structure of the larva, pupa and adult and in habits. That the habits of the two ants are totally different will be seen from a comparison of the observations above recorded with what we know of CEcophylla, and its various subspecies and varieties, which are arboreal ants inhabiting peculiar nests made of leaves and silk spun by their larvae. Still it may be objected that such ethological peculiarities have little significance, since we have species of Camponotus that i Dr. W. M. Mann, who has just returned with the Mulford Expedition from Bolivia, informs me that he found Gigantiops nesting under stones in the forests of the Rio Beni. OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. igi live in similar nests (C. senex Smith and formiciformis Forel) and others that live in the ground or in rotten logs (C. maculatus Fabr. and herculeanus DeGeer) . Turning to morphological char- acters, which the taxonomist regards as much more reliable, we find that the only resemblances between Gigantiops and CEcophylla (apart from the shape of the gizzard which both share with Cam- ponotus) are the shape of the clypeus, with its great, projecting lobe, the shape of the mandibles, and the feeble characters cited'by Forel* There are great differences in the size of the eyes and claws, in the shape of the thorax and petiole of the worker, and in the size and shape of the thorax of the female, though. the venation of the wings is similar. The larva of Gigantiops is like that of Camponotus, but very different from that of CEcophylla, and the pupa is inclosed in a cocoon. Probably the male Gigantiops will be found to exhibit some peculiar differences. Emery (in lift.} calls my attention to the singular fact that the tarsal claws of the male CEcophylla are almost completely atrophied. It would there- fore be very interesting to know the condition of these organs in the corresponding sex of Gigantiops. The foregoing considera- tions seem to me to render it advisable to remove Gigantiops from Forel's tribe (Ecophyllini and to provide an independent tribe for its accommodation. I find that Ashmead in 1905 had created such a tribe " Gigantiopini," though he included it in a subfamily Geso- myrmicinse, with Gesomyrmex and Myrmoteras, genera which, in my opinion, are only remotely related to Gigantiops. It is practically certain that Gigantiops is one of a number of ancient, large-eyed, active Formicinse, once of very wide distribu- tion, but now narrowly confined to the tropics. This group, which embraces also the genera CEcophylla, Dimorphomyrmex, Geso- myrmex, Opisthopsis, Santschiella, and Myrmoteras, represents merely the surviving specialized tips of diverging branches of a primitive stock. In regard to CEcophylla, Gesomyrmex, arid Di- morphomyrmex, we are actually in possession of considerable paleontological information. Mayr ('68), Emery ('05), and I ('14) have recorded the occurrence of two species of each of these three genera in the Baltic amber, of Lower Oligocene age ; Emery ('91) has recorded an CEcophylla and a species allied to Gesomyr- mex (Sicelomyrmex Wheeler) from the Sicilian amber, which is IQ2 WILLIAM MORTON WHEELES. referred to the Middle Miocene; Forster ('91) a species of CEco- phylla from the Middle Oligocene of Alsace, and Heer ('49) and Mayr ('67) two species from the Lower Miocene of Croatia. 1 More recently Cockerell ('20) described a species of this genus from the Eocene of England, and he ('15) and Donisthorpe ('20) three species from the Middle Oligocene of the same country. The one, or possibly two, extant species of (Ecophylla are now confined to the hottest portions of the Ethiopian, Indo- malayan, and Papuan Regions. Similarly the few extant species of Gesomyrmex and Dimorphomynnex are known to occur only in Borneo and the Philippines. 2 In the same regions and in Burma we find the four species of Myrmoteras. Santschiella is known only from a single specimen taken in the Belgian Congo, the species of the genus Opi'sthopsis are confined to the Aus- tralian and Papuan Regions, and the Neotropical Region possesses only one of these ancient large-eyed Formicines, Gigantiops. This, as we have seen, has a rather limited range and is in all prob- ability a true tropical relict, originally developed in and since mainly confined to that portion of the ancient South American con- tinent known as Archiguiana. All of the genera above mentioned are forest ants and most of them are arboreal, but, as we have seen, Gigantiops spends most of its time on the forest floor and nests in small, partly decayed logs. Opisthopsis nests under bark, in the ground or in earthen termitaria, and I may add that Dr. F. X. Williams, who took the types of Myrmoteras williamsi Wheeler in the Philippines, informs me that this ant nests in the soil. From what we know, therefore, of the living and extinct forms, we are justified in concluding that the large-eyed Formicinse originated during the early Tertiary, or more probably during the Cretaceous, and that the extant forms have since undergone little or no modification, owing to the very stable ecological conditions in which they were able to survive. Gigantiops, in particular, may * Since the completion of this paper Professor Cockerell ('21) has described a peculiar large-eyed ant from the Green River Eocene of Wyoming as Eoform- ica eocenica. It seems to belong to the subfamily Fomicinse and resembles the Australian Opisthopsis in the shape of the head and the position of the promi- nent eyes. 2 Since this paper was written I have published the description of a Gesomyrmex (G. howardi) from China. OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. 193 be said to have an even more remote origin than the archaic though highly specialized Neotropical vertebrates, such as the opossums, manatees, sloths, armadillos, ant-eaters and tapirs among mammals, or the ostriches and hoatzins among birds. The jumping or leaping habits of Gigantiops are so unusual that a more general account of this behavior as it occurs in various Formicidse may not be out of place. There are two very different kinds of leaping ants, one which I shall call " retrosalient," which always leaps backward, and one that may be called " prosalient," because it always leaps forward. Some authors regard the former as not " leaping," in the proper sense of the term, probably because of the direction and because it is not performed by means of the legs. But such very abrupt displacements of the body afe'effected in so many different ways in different insects, as, e.g., in Elaterid beetles, Lepismids, Collembolans, cheese-maggots, fruit fly and VermUeo larvee, the extraordinary Coleopteran (?) cocoons de- scribed by Berlese ('20, p. 631), etc., that such words as "leaping" can hardly be avoided without pedantry. We even speak of fish or of a cataract "leaping." Retrosalience has been repeatedly observed in two quite unre- lated groups of ants, one embracing the Ponerine genera Odonto- machus and Anochetus, the other the Myrmicine genus Stru- migenys. By convergence both of these groups have developed very similar long, straight, and linear mandibles, inserted close together on the front of the head and furnished with large, abruptly incurved teeth at their tips. When excited these ants open their mandibles so widely that they stand out at right angles to the long axis of the head or are even directed slightly backwards. And if one of the insects comes in contact with a solid object in its path, it closes them so suddenly and with such force that they make an audible "click" and the insect is thrown backwards through the air to a distance of several inches. I have described this behavior in detail in 0. clarus of Texas ('oo). It has also been observed in 0. chelifer of Brazil by Schupp (Wasmann, '92) and in the common tropicopolitan 0. hamatoda by Nietner ('58), Ferguson (Wroughton, '92), Forel, myself, and others. 1 The method of i Borgmeier ('20) has recently described the similar habits of 0. affinis in Brazil. " They strike their mandibles against the solid substratum and at the same moment leap 30 to 35 cm. vertically into the air." IQ4 WILLIAM MORTON WHEELER. leaping in Anochetus is precisely similar, as shown by the observa- tions of Wroughton ('92) on A. sedillotii var. indicus of India, and of Biro (Emery, '97) on a Papuan species. Among the Dace- tonini it has been observed by Hetschko in the Brazilian Stru- migenys saliens (Mayr, '93) and by 'Biro ('97) in 5". chyzeri Emery ('97) of New Guinea. The worker of the latter species is able to leap backward to a distance of 20-25 cm., or about 100 to 150 times the length of its body, but this behavior is not ex- hibited by the female. Forel ('93) believed that the Neotropical Acanthognathus ocellatus Mayr and Daceton armigerum Latr. might be able to leap in the same manner. I have failed to observe the habit in the allied Australian ants of the genus Orectognathus. All the retrosalient ants, however, leap rather reluctantly and only under certain conditions, and the length of their leaps varies directly as the degree of solidity of the objects against which they happen to close their mandibles. Prosalience is exhibited by at least three very different groups of ants : certain bull-dog ants of the Australian genus Myrmecia, Gigantiops, and the extraordinary genus Harpegnathos, or Dre- panognathus, as it was formerly designated, of the Indomalayan Region. The leaping Myrmecias, popularly known as " jumpers " in Australia, comprise the members of Emery's subgenus Pristo- myrmecia (fulvipes Rog., mandibularis Sm., and piliventris Sm.) and the smaller species of Myrmecia sens. str. allied to nigrocincta Sm. and pilosula Sm. I have frequently seen these ants jump distances varying from one to a few inches. When disturbed M. nigrocincta and pilosula, especially, present a ludicrous appearance as they bound out of their small mound nests- in a series of short hops like Lilliputian cavalry galloping to battle. Examination of these ants reveals a structural peculiarity which has .been over- looked by previous observers, namely, a distinct elongation and basal incrassation of their hind femora, as compared with the hind femora of the other nonsalient species of the genus. In Fig. 2 the hind femur of a worker M. nigrocincta (c) and that of a small worker of M. sanguinea of the same size (d) are drawn to the same scale. The greater length and volume of the femur of the former species shows a distinct approach to the conditions in the OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. 195 saltatory Orthoptera and is evidently to be interpreted as an ar- rangement for the accommodation of a more voluminous and there- fore more efficient extensor, or abductor muscle in the hind leg. This morphological peculiarity, together with the leaping habit, seem to me to be sufficient to justify a separation of these jumping species from the remaining Myrmecias as a distinct subgenus, for FIG. 2. Femora in profile and cross section of five species of ants drawn to the same scale, a. Gigantiops destructor; b, Componotus castaneus amer- icanus Mayr ; c, Myrmecia nigrocincta Smith ; d, small Myrmecia sanguined Smith ; e, Harpegnathos saltator Jerdon. which the name Halmamyrmecia subgen. nov. (with pilosula F. Smith as subgenotype) may be proposed. In Gigantiops I find an even more pronounced elongation and basal incrassation of the hind femur than in Pristomyrmecia or Halmamyrmecia. As there is only one species of Gigantiops, I have compared its hind femur (Fig. 20) with that of a non-leaping Camponotus worker of the same size (b). It will be seen that the difference in the length of the two femora is very pronounced, 196 WILLIAM MORTON WHEELER. but that the difference in the basal incrassation is not so striking when the parts are seen from the side. The shapes of the cross- sections of the bases of the two femora-, nevertheless, show that the Gigantiops femur is much more voluminous and therefore capable of furnishing attachment for a much larger and more powerful extensor muscle, as in the crickets and grasshoppers. FIG. 3. Female of Harpegnathos saltator Jerdon (after Mayr.). a, dorsal view ; b, lateral view ; c, head of same from above. Extraordinary feats of leaping are performed by the species of Harpegnathos, a genus confined to Indochina and the Philippines. In these ants (Fig. 3) the structure of the head is very singular, the eyes being very large, larger, in fact, than in any other Ponerine, and placed very far forward, and the mandibles are quite unlike those of any other known species. They are very long, separated at the base but approximated, arcuately curved upward, and gradually tapering toward their tips and finely serrate along their inner borders. Each is provided at the base with a large, flat, triangular tooth, projecting inward and somewhat downward and backward. In cabinet specimens the blades of the mandibles are applied to one another and the basal teeth overlap. The leaping habits of this insect have been observed by Lefevre, OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. -197 Lewis ('82), Wroughton ('92), and Bingham ('03). Lefevre states that it can make leaps of 20 to 25 cm., and Lewis saw it rise into the air to a height of 5 or 6 inches till exhausted, when its leap did not exceed an inch. Wroughton says : " The single speci- men of the genus, which I have had the luck to find, made leaps of a foot or 18 inches with perfect ease, exactly like a grasshopper. I had much trouble in securing this specimen, and, when I suc- ceeded, I found she could sting better than she could leap." Un- fortunately we have no observations on the modus saltandi of this curious insect. Its hind legs are really very short and even thinner than those of many nonsalient ants as indicated in the figure of the hind femur of a worker H. sdtator Jerdon (Fig. 2e}. As this ant is nearly of the same size as the specimens selected for the other femora (o-rf), and as the outline is drawn to the same scale,- it will be evident that no such feats of leaping as described by Wroughton can be performed with such appendages. We must conclude, therefore, that the mandibles are employed for this pur- pose, but how they function is a matter of pure conjecture till the living insect can be carefully studied. It is conceivable that when about to leap the Harpegnathos opens her mandibles slightly till the two basal teeth just barely touch, and that she presses the tips of the mandibles against the ground so that their long, slender, and probably very elastic blades are more arcuately bent. We may suppose, moreover, that if the two teeth are suddenly permitted to slide over each other, with a concomitant sudden unbending of the mandibles, the insect would be precipitated forward much like a very elastic strip of metal or whalebone bent in an arc and sud- denly released. It is less probable that the insect leaps by insert- ing the tips of the mandibles in the ground and bending them in the opposite direction, i.e., by more nearly straightening them and then suddenly allowing them to return to their original curvature. 1 i Since this paragraph was written I find that Professor Forel (1921, p. 47) gives some notes on the method of leaping employed by Harpegnathos. He states, apparently on the authority of some correspondent in India or China, that this ant " fait des bonds formidables de plus d'un metre a 1'aide de ses longues mandibules un peu recourbees en haut. La tete entiere se recourbe sous le corps, se rejettant ensuite en avant, un peu a la maniere du thorax de nos insectes d'Europe nommes taupins." 198- WILLIAM MORTON WHEELER. In conclusion, two interesting matters of a more speculative nature may be briefly discussed : 1. The various macrophthalmic, or large-eyed, tropical ants mentioned in this paper, namely, the Formicine genera Gigantiops, Opisthopsis, CEcophylla, Gesomyrmex, Dimorphomyrmex, Scmt- schiella and Myrmoteras, the Ponerine genera Myrmecia and Harpegnathos, and I may add also the whole subfamily Pseudo- myrminse, constitute only a small percentage of the more than 10,000 extant species, subspecies, and varieties of Formicidse. In the great majority of forms the eyes and ocelli of the female, and especially of the workers, have undergone considerable reduction in size or have entirely disappeared. In the male, however, which is the more conservative sex in ants, the eyes and ocelli are always large. These facts, together with what is now known of the ants of the Baltic amber, suggest that not later than Cretaceous time the females and workers were also all large-eyed, like the Scoliidoid wasps from which the Formicidee are derived, and that they pre- served this condition till after the social habit and a wingless worker caste had been evolved. During the Eocene and owing to the further development of the peculiar nesting and foraging habits, the females and workers became increasingly microphthal- mic and anophthalmic till the small-eyed or blind condition became established in the majority of existing forms. 2. It will have been noticed that all the known prosalient ants have very large, convex, and minutely faceted eyes, and that all belong to archaic genera. I have already discussed the antiquity of Gigantiops. The Myrmecias are, I believe, justly regarded as the most primitive of existing ants, survivors, without more than specific diversification, from the early Eocene or the late Creta- ceous. Harpegnathos includes only a few rare species of very restricted geographical range, evidently relicts on the verge of extinction. It would seem, therefore, that the leaping habit may have been much more general among the most ancient macroph- thalmic Formicidse, but had been abandoned as incompatible with a more highly developed social organization. This seems to be shown even within the genus Myrmecia, the larger and more domi- nant species of which no longer leap. That this habit should still persist, probably in a degenerate stage, in a few large-eyed forms, OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. .199 may be due to the fact that ants endowed with unusual visual powers can retain such a habit .with some impunity. Santschi ('u) and Brun ('14) have shown that vision is an essential factor in the homing behavior of ants that do not adhere very strictly to the topochemical trail made by themselves or their fellows from and to the nest. The leaping habit, if preserved and assiduously practiced in small-eyed ants, would, of course, often render it difficult or impossible to find the nest by means of the antennal sense alone. 1 LITERATURE. Ashmead, W. H. '05 A Skeleton, of a New Arrangement of the Families, Subfamilies, Tribes and Genera of the Ants, or the Subfamily Formicoidea. Canad. Ent., 1905, P'P- 381-384. Berlese, A. '20 Gli Insetti, Vol. 2. Milan, Soc. Edit. Libraria. 1920. Bingham, C. F. '03 Ants and Cuckoo Wasps. Hymenoptera, Vol. 2. In Blanford's Fauna of British India, including Ceylon and Burma. London, Taylor and Francis, 1903. Biro, L. 'gya Pattago hangyak (Jumping Ants). Rovart. Lapok., 4, 1897, pp. 73, 74. *97b Biologische Mittheilungen aus New Guinea. Ill Springende Ameisen. Berliner Ent. Zeitschr., 42, 1897, pp. 136, 137. Borgmeier, T. '20 -Zur Lebensweise von Odontomachus affinis Guerin. Ihering-Festschrift. Zeitschr. Ver. Wiss. Kunst, 1920, pp. 31-38. Brun, R. '14 Die Raumorientierung der Ameisen und das Orientierungsproblem im allgemeinen. Jena, Gustav Fischer, 1914, viii + 284 pp., 51 figs. Cockerell, T;. D. A, '15 British Fossil Insects. Proc. U. S. Nat. Mus., 49, 1915, pp. 469-499, 6 pis. '20 Fossil Artho'pods in the British Museum, I. Ann. Mag. Nat. Hist. (9), 5, 1920, pp. 273-279, 3 figs. '21. Some Eocene Insects from Colorado and Wyoming. Proc. U. S. Nat. Mus., 59, 1921, pp. 29-3.9, i pl-. 9 text-figs. Donisthorpe, H. S. J. K. '20 British OligO;cene Ants. Ann. Mag. Nat. Hist. (9), 6, 1920, pp. 81-94, i pl. ' i The mollusks of the genus Pecten are interesting in this connection, since, as is well known, they are able to leap considerable distances through the water by rapidly opening and' closing the valves of the shell and have their mantle margins beset with large, highly specialized eyes. 2OO WILLIAM MORTON WHEELER. . Emery, C. '91 I.e Formiche dell 'ambra siciliana nel museo mineralogico dell Univer- sita di Bologna. Mem. R. Accad. Sc. 1st. Bologna (5), i, 1891, pp. 141-165, 3 pis. '93 Zirpende und springende Ameisen. Biol. Centralbl., 13, 1893, pp. 189, 190. '97 Formicidarum Species Novae vel minus Cognitaa in Collectione Mussei nationalis Hungarici, quas in Nova Guinea, Colonla Germanica, col- legit L. Biro. Termeszetr. Fiizetek 20, 1897, pp. 571-599, 2 pis. '05 Deux Fourmis de 1'Ambre de la B'altique. Bull. Soc. Ent. France, 1905, PP- 187-189, 2 figs. Forster. '91 Abh. Geol. Spezialk. Els. 3, 1891. Forel, A. "78 Etudes Myrmecologiques en 1878. Bull. Soc. Vaud Sc. Nat., 15, 1878, PP- 337-392, i pi. '93 Observations Nouvelles sur la Biologic de Quelques Fourmis. Bull. Soc. Vaud Sc. Nat. (3), 29, 1893, pp. 51-53. '930 Sur la Classification de la Famille des Formic'ides avec Remarques Synonymiques. Ann. Soc. Ent. Belg. 37, 1893, pp. 161167. '12 Formicides Neotropiques. Part VI. Mem. Soc. Ent. Belg. 20, 1912, pp. 59-62. '17 Cadre Synoptique Actuel de la faune universelle des Fourmis. Bull. Soc. Vaud Sc. Nat., 51, 1917, pp. 229-253. '21 Le Monde Social les Fourmis. Tome. I. Geneve, Kundig, 1921. Heer, 0. '49 Die Insektenfauna der Teriargebilde von Oeningen und von Radoboj in Croatien. II Neue Denkschr. Schweiz. Ges. Na-turw., n, 1849, pp. 1-264, 17 pis. Lefevre. (Letter on Drepanognathus.) Ann. Soc. Ent. France (6), 3, p. LXXXIII. Lewis, G. '82 (Letter on Histeridae, etc.). In Nouvelles et Faits Divers. L'.Abeille (4), 2, 1882, p. 155, 156. Mann, W. M. '16 The Ants of Brazil. Bull. Mus. Comp. Zool., 60, 1916, pp. 339-490 7 pis. Mayr, G. '67 Vorlaufige Studien fiber die Radoboj-Formiciden. Jahrb. K. K. Geol. Reichsan., 17, 1867, pp. 47-62, i pi. '68 Die Ameisen des baltischen Bernsteins. Beitr. zur Naturkunde Preus- sens. I. K. Phys. Oekon. Ges. Konigsb., 102 pp., 5 pis., 1868. '86 Notizen fiber die Formiciden-Sammlung des British Museum in Lon- don. Verh. zool. bot. Ges. Wien., 1886, pp. 353-365. '87 Siidamerikanische Formiciden. Verh. zool. bot. Ges. Wien., 37, 1887, pp. 5"-532. '93 Erganzende Bemerkungen zu E. Wasmann's Artikel fiber springende Ameisen. Wien. Ent. Zeitg., 12, 1893, p. 23. OBSERVATIONS ON GIGANTIOPS DESTRUCTOR. 2OI von Motschulsky, V. '55 Lettre a M. Menetries in Motschulsky's " Etudes Entomologiques," 1855, pp. 8-38. "59 Briefliche Notiz iiber springende Ameisen. Stettin. Ent. Zeitg., 20, 1859, p. 201. - Nietner, J. '58 Uber eine springende Ameise in Ceylon. Brief an Chr. Drewsen. Stet- tin. Ent. Zeitg., 19, 1858, pp. 445, 446. Roger, J. "63 Verzeichniss der Formiciden-Gattungen und Arten. Berlin, A. W. Schade, 1863. Santschi, F. 'n Observations et remarques critiques sur le mecanisme de 1'orientation chez les fourmis. Rev. Suisse, 19, 1911, pp. 303-338, 6 figs. Smith, F. '58 Catalogue of Hymenopterous Insects in the Collection of the British Museum. VI. Formicidse, 1858, 216 pp., 14 pis. Wasmann, E. . '92 Einiges uber springende Ameisen. Wien. Ent. Zeitg., n, 1892, pp. 3i6-3i7. Wheeler, W. M. 'ob A Study of Some Texan Ponerinse BIOL. BULL., 2, 1900, pp. 131, 10 figs. '14 The Ants of the Baltic Amber, Schr. Physik. *fekon. Ges. Konigsb., 55, IPM, PP. I-I44, 66 figs- '17 The Australian Ant-Genus Myrmecorhynchtis (Ern. Andre) and its Position in the Subfamily Camponotina:. Trans. Roy. Soc. Austral., 41, 1917, pp. 14-19, i Pi- '18 The Ants of the Genus Opisthopsis. Bull. Mus. Comp. Zool., 62, 1918, PP- 343-362, 3 pis. Wroughton, R. C. '92 Our Ants. Part I. Journ. Bombay Nat. Hist. Soc., 1892, pp. 13-60, 2 pis.